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selinux: Re: bzip support in libsemanage and out of memory (user

Re: bzip support in libsemanage and out of memory (userspace ticket 7)

From: Stephen Smalley <sds_at_nospam>
Date: Mon Jan 25 2010 - 18:55:33 GMT
To: Guido Trentalancia <guido@trentalancia.com>


On Sun, 2010-01-24 at 21:29 +0100, Guido Trentalancia wrote:
> Hi !
>
> Has anybody had any time to look at this ticket:
> http://userspace.selinuxproject.org/trac/ticket/7 ?
>
> I have experienced the same issue and verified that the problem is actually triggered by the bzip support (as pointed out by Stephen Smalley back in August). In fact, if I use bzip-blocksize=0 in semanage.conf then the problem disappears...
>
> Otherwise with a default semanage.conf and bzip enabled, I get:
>
> libsepol.module_package_read_offsets: offset greater than file size (at 4, offset 200478 -> 8192 (No such file or directory).
> libsemanage.semanage_load_module: Error while reading from module file /etc/selinux/refpolicy/modules/tmp/base.pp. (No such file or directory).
> semodule: Failed!
>
> I am using libsepol-2.0.41 and libsemanage-2.0.42.

Looking into this more closely, I believe this is another manifestation of:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=543915#17

which was ultimately traced down to two issues: 1) A missing offset check in libsepol (fixed in libsepol 2.0.38), and 2) A bug / lack of binary mode support in the fmemopen implementation in glibc that was later fixed, see:
http://sourceware.org/bugzilla/show_bug.cgi?id=6544

Maybe you have the older glibc still?

Looking at the libsemanage code though, I think we could in fact avoid any dependency on fmemopen by using the native libsepol support for operating on a memory region via sepol_policy_file_set_mem(), ala:

diff --git a/libsemanage/src/direct_api.c b/libsemanage/src/direct_api.c index f09c7cf..fee6644 100644
--- a/libsemanage/src/direct_api.c
+++ b/libsemanage/src/direct_api.c
@@ -1371,16 +1371,12 @@ static int semanage_direct_list(semanage_handle_t * sh,

                 char *data = NULL;   if ((size = bunzip(sh, fp, &data)) > 0) { - fclose(fp); - fp = fmemopen(data, size, "rb"); - if (!fp) { - ERR(sh, "Out of memory!"); - goto cleanup; - } + sepol_policy_file_set_mem(pf, data, size); + } else { + rewind(fp); + __fsetlocking(fp, FSETLOCKING_BYCALLER); + sepol_policy_file_set_fp(pf, fp); } - rewind(fp); - __fsetlocking(fp, FSETLOCKING_BYCALLER); - sepol_policy_file_set_fp(pf, fp); if (sepol_module_package_info(pf, &type, &name, &version)) { fclose(fp); free(data);
diff --git a/libsemanage/src/semanage_store.c b/libsemanage/src/semanage_store.c index 0a55ce0..1b831bd 100644
--- a/libsemanage/src/semanage_store.c
+++ b/libsemanage/src/semanage_store.c
@@ -1528,16 +1528,12 @@ static int semanage_load_module(semanage_handle_t * sh, const char *filename,

         char *data = NULL;   if ((size = bunzip(sh, fp, &data)) > 0) { - fclose(fp); - fp = fmemopen(data, size, "rb"); - if (!fp) { - ERR(sh, "Out of memory!"); - goto cleanup; - } + sepol_policy_file_set_mem(pf, data, size); + } else { + rewind(fp); + __fsetlocking(fp, FSETLOCKING_BYCALLER); + sepol_policy_file_set_fp(pf, fp); } - rewind(fp); - __fsetlocking(fp, FSETLOCKING_BYCALLER); - sepol_policy_file_set_fp(pf, fp); sepol_policy_file_set_handle(pf, sh->sepolh); if (sepol_module_package_read(*package, pf, 0) == -1) { ERR(sh, "Error while reading from module file %s.", filename); -- Stephen Smalley National Security Agency -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@tycho.nsa.gov with the words "unsubscribe selinux" without quotes as the message.